The invention relates to a system for printing labels packaged on a continuous roll of backing material, and for automatically aligning the roll of labels in relation to the printer and controlling the printer to adjust settings and data to assure proper printing on the labels.
Adhesive labels are useful to attach text or graphics to articles that do not fit easily into a printer, do not have a surface that accepts ink well, or that may require changes or updating of labels. Blank labels are generally placed along a liner sheet or strip with their print surface facing away from the liner, being adhered to the liner by an adhesive that separably attaches them to the liner, which has a very low friction, non-adhesive surface. The label can be manually marked, or placed in a typewriter, but in commercial operations it is most commonly printed on by using a graphics printer; which can print, for example, images, bar codes, or text. Because of the characteristics of the liner and adhesive, the label is removable from the liner after printing, with the adhesive remaining with the label. The label then attaches securely by the adhesive with the print side displayed, to a material such as paper, cardboard, wood, plastic or metal.
An effective system for packaging blank labels affixes a number of labels, using a separable adhesive, to a continuous strip of low friction liner. This strip of label stock is wound around a tubular core to form a roll. Frequently, the label stock will be one label wide and many feet long, enabling sequential printing on many labels. Other configurations with two or more side by side, are also used. The width of the label stock is dependent on the size and disposition of the labels to be printed. The number of labels in a roll is generally limited to the capacity of the largest diameter roll a printing machine can accept. The roll typically is mounted in the printer on a spindle such that the label stock may be unrolled and fed through the printer as the labels are to be printed. The labels may be printed on demand, that is, one at a time; or a batch of labels may be printed in a continuous process.
Usually the spindle is positioned between upstanding legs of a pedestal, holding the roll of label stock in alignment with a paper insertion cavity in the printer. The roll is free to rotate around the spindle, so that the labels may be moved one at a time through the print mechanism by means of friction rollers driven by bi-directional electric motors. Inside the print mechanism is a print head which traverses the label along a scanning line transverse to the lengthwise direction of movement of the label stock. The print head may comprise any of a number of known printer mechanisms including an impact head acting on a ribbon, heating elements acting on thermal sensitive paper, and ink-jet array, or a laser or diode dry printer. The movements of the label stock and the print head are generally controlled by a microprocessor or other controller through driver motors which can provide relative positioning in two dimensions.
In order to properly use the label area, the printer must accurately align the label with the print head as to both the length and the width of the label. However, a printer usually must be able to prepare many different types of labels. Thus, the printer should be able to accept print label stock of different widths and materials, while maintaining alignment. The printer must have either a means to advance the roll of label stock in proper position or compensating mechanisms to properly feed the label stock into the print mechanism. An erratic off-center roll location leads to errors in placement or feeding and requires mechanisms or software to properly align or control the feeding of the labels into the printer. Such compensating mechanisms may be complicated and increase the effort required of the operator to load the roll of label stock into the printer.
In order to print properly on labels of different lengths and widths, the printer preferably has some means for identifying the geometry of the labels to the microprocessor controller. Traditionally this means has been an input keyboard through which an operator enters the information. Minor alignment corrections can be accomplished automatically by providing marks in the label stock, a sensor in the printer to detect the location of these marks, and a program within the controller to correct its commands to the driver motors.
Additionally, information about the type of labels in the roll must be entered into the microprocessor controller, for example, information as to the type of material from which the labels are made. This information may be used to determine the optimum temperature for heating elements within the printer, as for an ink-jet system. Traditionally this information also has been entered manually by an operator. Any information that must be entered manually increases the effort required of the operator and introduces an opportunity for human error.
The invention accordingly has an object of providing a system to accurately and conveniently align rolls of label stock of various widths with the print head in a label printer.
It is also an object of the invention to provide a system which automatically identifies the type and position of labels contained on a roll of label stock so that printing positions, geometries, and styles can be varied.
A system in accordance with the invention provides advantageous means for aligning labels relative to the print head in a printer in which a roll of label stock of any of a range of widths may be easily mounted on a printer spindle, while the roll is retained in a centered position through an interior mechanism. The system also ascertains the dimensions and location of the labels, by scanning the liner strip and indicia provided on the liner strip holding the labels. The system further provides an arrangement for automatically identifying to the printer particular parameters needed for printing, so that predetermined adjustments may automatically be made for best printing. The system reduces manual effort, decreases the chance for operator error, and provides error detection in the event of misplacement or coding errors.
The invention includes a system to center labels carried on a roll of label stock with respect to the print head of a printer even though the label stock is of some arbitrary width within an acceptable range. The labels are removably attached on a continuous liner strip wound about a tubular core that has a central or other discontinuity, such as a circumferential groove or protrusion. The printer spindle is of smaller outer diameter than the inner diameter of the core, and incorporates a central circumferential discontinuity, groove or ring, mating with a complementary discontinuity (ring or groove) on the inside of the core. The roll of label stock and labels is held by its own weight in the centralized position on the spindle as the label stock is unwound. The core is advantageously made as two tubular end elements joined by a central spacer of larger inner diameter defining a central groove, although the discontinuity may be at some other transverse position.
Further in accordance with the invention, indicia are included in the liner strip and an optical detector in the scanning head is disposed to detect those indicia and the strip width as the scanning head scans the strip. At least two types of indicia are used, one being a positional reference as to the label, and the being other encoding information needed to set control parameters in the printer if standard conditions are not to apply. The positional references, which may be holes in the liner, are placed in one margin in a predetermined location relative to each label end so that lengthwise label dimension can be determined. The code information is disposed in the other margin in positionally varied sets also referenced to the positioning holes, and may comprise a predetermined number of holes, lying at varying lengthwise positions in a number of predetermined locations. After scanning to derive the code information, the controller then retrieves commands from a look-up table in its memory for use in controlling the printing process. For example, with an ink-jet head the temperature of heating elements and the speed of printing may be controlled for best results. The distance from one label to the next is ascertained and compared to what it should be from the label description identity, and if it varies from the prescribed value or if the codes are not proper this information is used to stop the printer.
Methods in accordance with the invention incorporate a number of scanning steps to determine from the strip, and the indicia, data which verify at each label if desired that the labels are correct, the codes are properly sized and correct, and that certain printing conditions must be used. This information is converted into commands such that complex multicolor images can be placed on each label with assurance of reliable operation.